82 Reduction Phenomena in the Myxomycetes. 
NUCLEAR FUSIONS AND REDUCTION PHENOMENA 
IN THE MYXOMYCETES. 
I N the course of a cytological investigation of Ceratiomyxa, the 
sole representative of the exosporous Myxomycetes, Olive 
has obtained evidence that a fusion of nuclei in pairs occurs prior 
to spore-formation and that this fusion is followed by a synaptic 
stage and two nuclear divisions. The course of events described 
by Olive is as follows:—Fusion of nuclei in pairs occurs towards 
the close of the cleavage of the protoplasm which precedes spore- 
formation. The peripheral protoplasm is thus cut up into 
numerous uninucleate masses which may be called “ protospores.” 
Creeping movements now take place in these “ protospores ” so 
that each forms a swollen globular end borne on a long stalk. All 
the protoplasm passes into the globular extremities, the stalks and 
other supporting structures then consisting of nothing but slime. 
Olive states that the nuclear fusion referred to above is followed 
almost immediately by synapsis. His figures show clearly that 
a contraction of the chromatin thread takes place at this stage. 
Two nuclear divisions follow directly in rapid succession, but these 
being unaccompanied by cell-division, each spore at maturity 
contains four nuclei. Olive looks upon these two mitoses as 
comparable to the double nuclear division which occurs in spore- 
mother cells and with which reduction in the number of chromo¬ 
somes is associated. If this interpretation is correct the single 
“ spore ” of Ceratiomyxa represents a tetrad of spores of the higher 
plants. 
Jahn 2 states, however, that a nuclear fusion in Ceratiomyxa 
takes place at an earlier stage than that mentioned by Olive. 
The former describes a nuclear fusion in the young fruit bodies, 
this fusion being followed by a contraction of the chromatin 
which he interprets as synapsis. Shortly before spore-formation 
two nuclear divisions succeed one another in rapid succession and 
these Jahn considers to be the heterotype and homotype mitoses. 
Of the nuclei thus produced, Jahn states that at least half disorganise, 
while the others form the nuclei of the young spores. During the 
maturation of the latter two nuclear divisions succeed one 
another rapidly so that each ripe spore contains four nuclei as 
described by Olive. 
There is thus a marked divergence in the results of these two 
investigators. Unfortunately Jahn gives no figures, so it is 
impossible to compare adequately his results with those of Olive. 
The latter expressly states that he could find no nuclear divisions 
in the fructifying plasmodium prior to cleavage, and concludes that 
Ceratiomyxa is peculiar in this respect since in other Myxomycetes 
1 Olive, E. W. Cytological Studies on Ceratiomyxa. Trans. 
Wisconsin Academy of Sciences, etc. December, 1907. 
2 Jahn, E. Myxomycetenstudien—Kernverschmelzungen und 
Reduktionsteilungen. Ber. d. Deut. Bot. Ges., Feb., 1907. 
